ABSTRACT Pre-injury use of anticoagulant and antiplatelet medications is increasingly more common in older adults (55 years and older) with head trauma. Rapid diagnosis of intracranial hemorrhage (tICH) and reversal of anticoagulant effects is crucial in these patients to prevent significant morbidity and mortality. Gaps in knowledge regarding this high risk patient population, as specified by the RFA, include: data on the burden of disease (e.g., prevalence of tICH, neurosurgical interventions, long- term functional outcomes), the accuracy of medication ascertainment by emergency medicine services (EMS) providers, the accuracy of pre-hospital triage criteria to determine the need for 24- hour neurosurgical and intensive care monitoring, and the impact of pre-hospital triage to a trauma center on patient-oriented outcomes. These gaps in knowledge will be addressed through a prospective, longitudinal, county-wide study of older adults with pre-injury anticoagulant or antiplatelet and head trauma that are initially evaluated by EMS providers. The overall objective of this proposal is to improve patient-oriented outcomes for older adults with pre-injury anticoagulant or antiplatelet use and traumatic brain injury through accurate and effective field triage. The aims of this study are: 1) Describe the burden of disease in this patiet population 2) Compare the accuracy of existing and a novel method of medication ascertainment by EMS providers to identify use of anticoagulant or antiplatelet medications 3) Evaluate the utility of current triage criteria (including EMS clinical impression) and compare to newly derived set of criteria specific to this patient population 4) Compare long-term functional outcomes for patients initially triaged to a trauma center versus those triaged to a non-trauma center. We hypothesize a significant proportion of these patients will have poor long-term functional status after TBI, existing methods of medication ascertainment are inaccurate, existing triage criteria will undertriage a significant proportion of these patients, and patients triaged to a trauma center will have better long-term functional status compared to patients triaged to a non-trauma center. Long-term functional status will be determined from 6-month Extended Glasgow Outcome Scores (GOS-E), accuracy of medication ascertainment will be determined by comparison to a reference standard of in-hospital medication ascertainment, accuracy of triage criteria will be determined by the primary outcome of immediate tICH and the secondary outcomes of serious injury (Injury Severity Score greater than 15) and trauma center resource use (ICU admission, major non-orthopedic surgery, and/or in-hospital mortality).